1. Field of the Invention
The present invention relates to oil well pumping equipment and more particularly to a means for releasing the hydrostatic pressure contained by the tubing.
Oil well pumping equipment includes a string of tubing in a borehole having a vertically reciprocating fluid pump in its depending end portion operated by sucker rods. Some oil producing formations contain sand or other abrasive material which wears the pump components necessitating replacement of the pump by pulling the sucker rods and pump. Sometimes on account of equipment malfunction, sand sticking the pump or for other reasons the pump anchor hold down body cannot be separated from the anchor hold down shoe at the depending end of the tubing. This requires pulling the tubing and the sucker rods simultaneously and is known as a "stripping job" wherein oil within the tubing is wasted as each joint of tubing is disconnected at the surface of the earth besides creating a hazardous condition for workmen. Furthermore, the increased mass of the pumping string, as a result of the tubing contained fluid, requires the use of a heavy duty pulling unit and additional fuel for its operation.
2. Description of the Prior Art
Frangible disks closing a port in the wall of a tube in oil wells, and the like, are well known, however, these frangible disks have generally comprised a means for releasing valves or plugs for closing the bore of the tube to permit reverse circulation.
This invention provides a subjoint containing a port closed by a frangible disk disposed below the oil well pump which, when the disk is ruptured, drains oil out of the tubing into the borehole.